What does a 20% ingredient price rise do to restaurant margin?

A 20% rise on an ingredient worth 15% of sales removes 3.0 margin points

Start with the ingredient's cost in one standard portion. Do not apply 20% to the whole recipe.

Then update the plate.

Recalculate gross profit at the current ex-VAT selling price.

There is also a useful shortcut when the selling price and portion stay fixed.

An ingredient costing 15% of the ex-VAT selling price, rising by 20%, removes 3.0 percentage points: 15% × 20% = 3.0%.

One chicken line moves a dish from £4.00 to £4.42

The following Riverside Kitchen chicken dish is illustrative. It sells for £14.00 ex-VAT. The current standard portion costs are:

• Chicken: £2.10
• Rice, vegetables and sauce: £1.40
• Packaging: £0.50

The total portion cost is £4.00.

The supplier raises the chicken's normalised unit price by 20%. Portion size and measured yield do not change.

The whole plate cost rose by 10.5%, not 20%: £0.42 ÷ £4.00 × 100.

At the unchanged £14.00 selling price:

This is a 4.2% fall in cash gross profit per dish, because £0.42 is 4.2% of the old £10.00 gross profit. Percentage points and percentage change answer different questions.

The same 42p can reduce monthly net profit by 16.8%

The dish sells 1,200 portions in a month. The supplier increase adds:

Gross profit from that dish falls from £12,000 to £11,496 if volume and selling price stay fixed.

Suppose the restaurant previously expected £3,000 monthly net profit before tax after wages, rent, utilities and other costs. If every other figure stays unchanged:

The ingredient did not consume 16.8% of sales. It consumed 16.8% of a much smaller net-profit pool.

This bridge is illustrative, not a forecast. Customer demand, menu mix, waste, labour, commissions and other supplier prices also move.

A £14.42 price protects cash GP, but £15.47 protects the margin percentage

There are two different pricing goals. To keep the old £10.00 cash gross profit per dish, add the 42p cost increase:

That price produces a 69.3% margin, below the old 71.4%.

To keep the old 71.4% gross margin, solve from the new cost:

Neither figure decides the menu price alone. Check customer response, competitors, menu architecture, VAT treatment and the contribution needed to cover labour and overheads.

Broad inflation figures cannot price your own supplier basket

The Office for National Statistics reported that consumer food and non-alcoholic drink prices rose 1.3% in the 12 months to July 2026. Its restaurant and hotel category rose 4.0%.

Those are consumer-price measures, not your restaurant's supplier invoices. The ONS also explains that a category's contribution depends on both its price movement and its weight. Your dish works the same way: a supplier rise matters according to the ingredient's weight in sales and the number of portions sold.

The July 2026 producer-price release moved differently again. Domestic food inputs fell 1.6% over the year, while imported food inputs rose 1.0%. Those series cover manufacturing inputs. They do not prove what your chicken, oil or tomatoes should cost.

An unchanged case price can still hide a unit-cost rise

A supplier can hold a case at £48.00 while changing it from 10kg to 8kg.

The invoice total looks unchanged. The usable unit cost does not.

Involiqo stores reviewed invoice line items and can compare price, quantity, supplier and spending movement over time. Cost Watch can place the current unit price beside the previous period and show cost concentration. The operator still confirms pack descriptions, credits, substitutions and recipe mapping.

Rank price rises by monthly pounds at risk

The largest percentage rise is not always the first problem to solve.

For the chicken dish:

Suppose a garnish rises by 50%, but its old cost was £0.05 on the same 1,200 dishes:

The garnish has the louder percentage. The chicken has £474 more monthly exposure.

Review high-exposure lines first. Then choose whether to challenge the supplier, test another specification, reduce waste, adjust the portion, redesign the dish or change the selling price.

Frequently asked questions

Does a 20% food-cost rise mean menu prices must rise by 20%?

No. Calculate the cash increase in one portion, then decide what price change the dish can support. A 20% increase on one ingredient rarely means a 20% increase across the plate. Protecting the old cash GP needs a smaller price than protecting the old margin percentage. Demand and menu positioning still matter.

Should a restaurant use gross margin or markup?

Use gross margin when comparing gross profit with the ex-VAT selling price. Markup compares gross profit with cost, so it produces a different percentage. Write the formula beside the target. Otherwise, two people can discuss ‘70%’ while using different denominators and reach different selling prices.

What if the supplier price falls again next month?

Keep the new invoice evidence and recalculate the same bridge. Do not assume a rise or fall is permanent from one unusual delivery. Check the unit, pack, credit notes and substitute items. A rolling comparison shows whether the change repeats before you redesign a recipe or reset a menu price.

Key takeaways

1. Apply the price rise to the affected ingredient, not the whole dish.
2. A 20% rise on an ingredient worth 15% of sales removes 3.0 margin points.
3. The illustrative chicken dish loses 42p per portion and £504 per month.
4. Protecting cash GP and protecting margin percentage require different prices.
5. Rank supplier changes by monthly pounds at risk, not percentage alone.

Sources

1. Office for National Statistics: Consumer price inflation, UK, July 2026 — https://www.ons.gov.uk/economy/inflationandpriceindices/bulletins/consumerpriceinflation/july2026
2. Office for National Statistics: Producer price inflation, UK, July 2026 — https://www.ons.gov.uk/economy/inflationandpriceindices/bulletins/producerpriceinflation/latest
3. Involiqo: Cost Watch and item analytics — https://involiqo.com/#bento-overview

Recalculate one high-volume dish this Monday

Start with the supplier line showing the largest monthly spend. Confirm its normalised unit price, update one standard portion and multiply the cash change by last month's portions sold.

Use the true portion-cost method before repricing: https://involiqo.com/blog/cost-per-portion-restaurant. Check the theoretical-versus-actual food-cost bridge when usage still differs from the recipe: https://involiqo.com/blog/theoretical-vs-actual-food-cost. Use the restaurant net-margin guide before treating dish GP as final profit: https://involiqo.com/blog/uk-restaurant-net-profit-margin.

See how Involiqo turns reviewed supplier invoice lines into Cost Watch evidence: https://involiqo.com/#bento-overview.